The present invention relates to packaging films, and more specifically to packaging films useful in vacuum packaging applications.
Vacuum packaging, and particularly vacuum skin packaging has become an increasingly attractive way of packaging fresh red meats. The final package presents a tight fitting, clear package which protects the food article from the external environment. However, the demands imposed on the packaging material used in vacuum packaging, and especially in vacuum skin packaging, are high.
One particular problem which has presented a significant hurdle for the development of vacuum skin packaging has been implosion or breakage of the film during the packaging of fresh pork, broiled and browned pork, shingled turkey breast, and other food items. Generally, products that have cavities or undercuts are especially prone to implosions or leakers created by failure of the film during the vacuum skin packaging process. Using standard materials, package failures as high as 60% have occurred.
Thus, in actual practice, conventional films tend to be broken when subjected to the high stretch ratios at particular projections, undercuts or recesses present on the material being packaged.
To resolve this problem, it is an object of the present invention to provide a highly formable film which is nevertheless resistant to im-plosions created during the vacuum skin packaging process, and provides high abuse protection for the final packaged product.
Of interest is U.S. Pat. No. 4,469,742 issued to Oberle disclosing a multilayer film having the structure (inner) A/B/C/D/C/E (outer), where A is a bonding layer comprising an ethylene-propylene copolymer; B is a shrinking layer which may be formed from an ethylene vinyl acetate copolymer having a vinyl acetate content in the range of 6% to 12% by weight, preferably 6%; C are adhesive layers affected to join the barrier layer D to the remainder of the film. The layer D is formed from ethylene vinyl alcohol copolymer. The outer layer E isolates the barrier layer against contact with outside moisture and comprises an ethylene vinyl acetate copolymer having a vinyl acetate content ranging from 5% to 12%, preferably 6%, by weight.
UK Patent No. 1,271,995 (Gerow) discloses laminated oxygen barrier films including a formable base layer, hydrolyzed ethylene vinyl acetate, and a heat sealable layer such as EVA.
An object of the present invention is to provide a film which provides an oxygen barrier property for the preservation of food product such as meats adversely affected by oxidation.
Another object of the present invention is to control and limit the bridging phenomenon which can occur between adjacent forming stations in a VSP machine.
Yet another aspect of the present invention is to provide a film resistant to rupture induced in some thermoforming and VSP applications.
Still another object of the present invention is to provide a rupture-resistant film while possesses good optical properties.